M. Lezius et al., HOT NANOPLASMAS FROM INTENSE LASER IRRADIATION OF ARGON CLUSTERS, Journal of physics. B, Atomic molecular and optical physics, 30(7), 1997, pp. 251-258
Argon ions with charge states of at least up to q = 9 are produced wit
h 10(14) W cm(-2), 30 ps laser light pulses at 1064 nm from neutral Ar
, clusters, whereas only Ar3+ can be produced from monomers. Irradiati
on of cluster targets leads to ions with remarkably high kinetic energ
ies exceeding 4.8 keV, depending on the ion charge state. The experime
ntal results are understood in terms of cluster-sized nanoplasmas with
internal electron temperatures of approximately 7 x 10(6) K which are
heated by collisional electron-ion absorption. From these thermalized
superdense nanoplasmas highly charged ions are ejected isotropically
with the corresponding ion sound velocity. A simple Coulomb explosion
model cannot account for the observed ion energies.